Social networks can permit users to post information about themselves and communicate with other people, such as their friends, family, and co-workers. Some social networks permit users to specify friendships with other users. Additionally, social network users may write descriptions of their interests, compose stories, describe their lives, etc. Some user may generate a great amount of content, while other users may generate very little.
Some social networks permit users to watch videos, post comments about the videos, communicate with other users watching the videos, and share the videos with their friends. For example, YOUTUBE is such a social network. Advertisers may wish to target the users of social networks by placing advertisements so that they are along side videos watched by social network users.